When you are having anal with an Asian and right before climaxing you pull out and finish on their ass. Coating their butt cheeks in a snowy white residue.
1.
"Thank you for your snow skin mooncake, Catherine"
"As long as you like it, Ken. ^_^"
2.
"The Mid-Autumn Festival starts today! Would you like to celebrate by coming over to my place and enjoying a snow skin mooncake?"